As the illustration above shows the Sinhala leaders have no incentive to cater to Tamils or Muslims. And TNA or Tamils don’t gain anything by moving their position to the right of the scale. Are the Muslims also in their own distribution that is not aligned to the two above? If so, do they overlap more with the Sinhalese or with the Tamils?
There is nothing Tamils or Muslims do or say that will convince the Sinhala median voter to move to the left to meet them halfway as the median voter theorem dictates.